1. Field of the Invention
The present invention relates to a method of transmitting data, and more particularly, to a method of transmitting data in cellular networks using cooperative relaying.
2. Discussion of the Related Art
In the world of cellular telecommunications, those skilled in the art often use the terms 1G, 2G, and 3G. The terms refer to the generation of the cellular technology used. 1G refers to the first generation, 2G to the second generation, and 3G to the third generation.
1G refers to the analog phone system, known as an AMPS (Advanced Mobile Phone Service) phone systems. 2G is commonly used to refer to the digital cellular systems that are prevalent throughout the world, and include CDMAOne, Global System for Mobile communications (GSM), and Time Division Multiple Access (TDMA). 2G systems can support a greater number of users in a dense area than can 1G systems.
3G commonly refers to the digital cellular systems currently being deployed. These 3G communication systems are conceptually similar to each other with some significant differences.
A Broadcast Multicast Service (BCMCS) provides the ability to transmit the same information stream to multiple users simultaneously. More specifically, the BCMCS is intended to provide flexible and efficient mechanism to send common or same information to multiple users. The motivation for this service is to achieve the most efficient use of air interface and network resources when sending the same information to multiple users. The type of information transmitted can be any type of data (e.g., text, multimedia, streaming media). The BCMCS is delivered via the most efficient transmission technique based on the density of the BCMCS users, information (media type) being transmitted, and available wireless resources.
Transmission territory for each BCMCS program can be independently defined. Here, the BCMCS program refers to a logical content transmitted using the BCMCS capabilities. Moreover, the BCMCS program is composed of one or more internet protocol flows. In operation, the programs can be transmitted in time sequence on a given channel. The BCMCS programs can be transmitted to all or selected regions of the network. These regions constitute the transmission territory which refers to an area of wireless network coverage where transmission of a BCMCS program can occur. The transmission territory can be defined by a set of cells/sectors that can transmit a BCMCS program. In addition, the BCMCS programs can be received by all users or can be restricted to a subset of users via encryption.
In the BCMCS, retransmission and acknowledgement are not required since the type of transmission is “one way” and/or “one to many.”
The BCMCS subscription is normally associated with the program (e.g., ABC, TNT, ESPN), not the content (media type such as music, video, etc.). That is, by selecting the program, the user selects the type of content the user wishes to receive.
The BCMCS in cellular networks typically incur coverage holes and limited capacity (channels) per carrier. This can arise due to channel propagation impairments (e.g., severe shadowing), large cell sizes (e.g., with site-to-site distances greater than 2 km) due to high cost of base terminal station (BS) deployments, limited bandwidth, and interference from adjacent cells transmitting different BCMCS content. Consequently, BCMCS coverage becomes limited along with broadcast multicast system capacity.
Further, in contrast to the conventional unicast services, the performance of the BCMCS is determined by the reception quality of the users located at the edge of the coverage area.